Tailored tubular blanks and a method for the production thereof

ABSTRACT

To make tailored tubular blanks the circumferential weld seam and the longitudinal weld seam are so arranged that the seams do not intersect but only form an interface. In this way tailored tubular blanks that have better formability are produced.

Applicants hereby claim foreign priority benefits under 35 U.S.C. § 119of Swiss Patent Application No. 522/00 filed 23 March 2000 and PCTApplication No. PCT/CH0 1/00122, filed 26 February 2001, the disclosuresof which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to tailored tubular blanks and methods formanufacturing them in general, and in particular to tailored tubularblanks having at least one circumferential weld seam and at least onelongitudinal weld seam, and methods for manufacturing the same, inparticular.

2. Background Information

Tailored tubular blanks are welded open-ended bodies either in the shapeof a simple tube, or alternatively with a non-circular cross-section ora cross-section that varies along the length, which can result in acylindrical or conical or irregular form lengthways. The shape given tothem depends on their subsequent intended purpose and is designed withthe latter in mind. For simplicity's sake these bodies, including thosethat are irregularly shaped, will be referred to as “tubes”. Tailoredtubular blanks are characterised by the fact that they are made from twoor more metal sheets of different thickness and/or grades of materialand/or coatings. The way in which such tailored tubular blanks areconstructed from metal sheets with different characteristics producestubes the sections of which are specifically adapted to the requirementsconcerned. These tailored tubular blanks may be used as such or in themain example of their use further processed by shaping them, notablyusing hydraulic shaping (hydroforming), to make hollow bodies withcomplex shapes. Such hollow bodies or shaped parts are for instanceemployed in automotive engineering, for example as load-bearingcomponents in the vehicle body (pillars, roof rail, sill beam sections,etc.) and in the undercarriage (running gear, chassis rails,cross-members, muffler and catalyst housings, etc.). Application fieldsother than automotive engineering are also possible, notably whereverspatially complex specialist parts are to be employed. The specialistterm “tailored tubular blanks” is used generally in the technicalterminology and therefore also in this patent application; by analogywith the conventional plane “tailored blanks” (rendered in German interalia as “belastungsangepasste Platinen”), “tailored tubular blanks” mayinter alia be rendered in German as “belastungs-angepasste Rohre”.

Tailored tubular blanks are joined using beam welding techniques (laserwelding, electron beam welding or resistance arc welding), involvingfirstly rounding a tailored blank in the conventional way to make atube, and then making the weld seam longitudinally along the tube. FIGS.1 a-1 c and 2 a - 2 c show two different variants of tailored tubularblanks taken from the prior art. FIGS. 1 a-1 c show a first varianthaving parallel longitudinal seams, with FIG. 1 a showing the planetailored blank 1 from metal sheets 1 and 2 with the weld seam 3. FIG. 1b shows the welded tube (tailored tubular blank) from above with thetube's longitudinal weld seam 4, and FIG. 1 c shows a cross-sectiontaken through the tube. The present invention does not relate to suchtailored tubular blanks having weld seams running exclusivelylengthways, but to tailored tubular blanks as seen in FIGS. 1 a- 2 cwith a circumferential and a longitudinal seam. FIG. 2 a shows thecorresponding tailored tubular blank with the metal sheets 1 and 2 andthe weld seam 3, which after being formed into a tube as shown in FIG. 2b (tailored tubular blank) forms the circumferential weld seam 3 whichintersects the weld seam 4 running the length of the tube. FIG. 2 cshows a cross-section through such a tailored tubular blank in theregion of metal sheet 2. Tailored tubular blanks with a transversedivision, as shown in FIGS. 2 a -2 c, can exhibit drawbacks during thesubsequent shaping operation (e.g. hydroforming) because the weldingstresses are concentrated at the point of intersection and theheat-affected zones (the margins of the weld zone proper) of the twoseams overlie one another. There is also an increased risk of weldingdefects at the point where the seams intersect. By controlling thewelding process to maximum effect it has up till now been attempted toavoid these drawbacks as far as possible, or at least to minimise themto the extent that they make no difference in the metal formingoperation. However, depending on the characteristics of the metal sheetsit is difficult to select and observe suitable welding parameters.

DISCLOSURE OF THE INVENTION

It is therefore the object underlying the invention to create tailoredtubular blanks having a circumferential seam and a longitudinal seamwhich do not incur the stated drawbacks or at any rate only to a greatlyreduced degree.

In the case of tailored tubular blanks of the type mentioned in theintroduction, this object is achieved by a tailored tubular blank thathas at least one circumferential weld seam and at least one longitudinalweld seam, wherein the circumferential weld seam and the longitudinalweld seam do not intersect one another when they meet at the joint.

The fact that the circumferential seam (or circumferential seams if morethan one is provided) do not intersect the longitudinal seam (orlongitudinal seams if more than one is provided) means that theaforementioned drawbacks are largely not applicable. Non-intersectingseams merely abut one another, with the result that they may be referredto concretely as T-joints, although as a rule the seams do not meet at aright angle. Such T-joints have a low concentration of welding stressesin the vicinity of the welded joints than is the case with intersectingseams, which results in better formability. Also the risk of weldingdefects when joints are being welded is smaller than when weldingintersecting seams. The interfaces of the seams can also be moresystematically positioned at locations that are subject to little stressin metal-forming terms.

It is a further object of the invention to create a process forproducing tailored tubular blanks that do not have the stated drawbacks.

This object is achieved by a process for, or method of, making atailored tubular blank that has at least one circumferential weld seamand at least one longitudinal weld seam, wherein the circumferentialweld seam and the longitudinal weld seam are arranged in such a mannerthat the seams meet at a joint.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be explained in detailwith reference to the Figures, wherein:

FIGS. 1 a-1 c show a tailored blank, a tailored tubular blank in a planview and a cross-section through the latter under the prior art;

FIGS. 2 a -2 c also show a tailored blank, a tailored tubular blank anda cross-section under the prior art;

FIGS. 3 a -3 c show a first exemplary embodiment of the invention,likewise with a tailored blank, a tailored tubular blank and across-section;

FIGS. 4 a -4 c show a further exemplary embodiment, in which tubularsections are joined at their ends;

FIGS. 5 a and 5 b show a further exemplary embodiment with a tailoredblank and tailored tubular blank in a plan view;

FIGS. 6 a and 6 b show a further exemplary embodiment with a tailoredblank and tailored tubular blank;

FIG. 7 shows an exemplary embodiment of a tailored blank; and

FIG. 8 shows another exemplary embodiment of a tailored blank.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 a-1 c show an example, already explained above, of prior arttailored tubular blanks the embodiment of which does not form asubject-matter of the present invention. FIGS. 2 a -2 c show anexemplary embodiment of prior art tailored tubular blanks having alongitudinal seam and a circumferential seam, the improved version ofwhich does form a subject-matter of the present invention.

FIG. 3 a shows a first exemplary embodiment of tailored tubular blanksin accordance with the invention, with FIG. 3 a showing the tailoredblank 10 from which the tubular can body will be shaped, using anyconventional tube shaping process, and then welded to make the tube. Thetailored blank 10 is formed by welding two metal sheets 11 and 12 whichare joined to one another by means of a diagonal weld seam 13. The metalsheets 11 and 12 may be any desired conventional metal sheets ofdifferent thickness and/or with different sheet metal characteristics,as is fundamentally known in making tailored tubular blanks. When thetailored blank is formed into the tube by working the edges 16 and 17 ofthe tailored blank out of the drawing plane and away from the observer,the result is a tubular can body as in the plan view seen in FIG. 3 b,in which the edges 16 and 17 have already been joined together by a weldseam 18. The weld seam 13, which runs at the end points 14 and 15 intothe edges, 16 and 17 respectively, then forms with the weld seam 18 twointerfaces, 14 and 15 respectively, which are spaced apart from oneanother by a predetermined distance. The spacing results from theoblique position of the weld seam 13 and can be selected in acorrespondingly free manner and, for example, be from a few millimetresto several centimetres in size. This means that each end of weld seam 13is only butted up to weld seam 18 and does not continuously intersectthe latter, which brings about the advantages outlined above. FIG. 3 cshows a cross-section through the tube 20 in the vicinity of the metalsheet 12.

FIGS. 4 a -4 c show another form of embodiment of tailored tubularblanks in accordance with the invention, exemplified by depicting a tube30 which has a continuous circumferential seam 33 adjoined by twolongitudinal seams 31 and 32 which do not intersect at the joint, withthe interfaces being identified as 34 and 35 respectively. Here, too,the interfaces are spaced a preselected distance apart from one another.FIG. 4 c shows the two tubes 36 and 37 which serve as starting partswith longitudinal weld seams 31 and 32 for tailored tubular blanks asseen in FIG. 4 a. The tubes 36 and 37 are preferably in turn constitutedby metal sheets of different thickness and/or having different materialcharacteristics. The tubes 36 and 37 are then joined togethercontiguously with one another by welding the continuous circumferentialseam 33, thereby producing the tailored tubular blanks as seen in FIG. 4a. FIG. 4 b shows a cross-section taken through the tailored tubularblank 30 from FIG. 4 a, in the vicinity of the tube 37. Unlike the perse known construction of tubes from tube sections, where as a rule thelongitudinal seams are in alignment with one another but there may begreater or lesser or undefined deviations in the alignment of thelongitudinal weld seams due to inaccuracies in the production process,in the present case relating to the construction of tailored tubularblanks the starting tubes 36 and 37 are deliberately joined togetherwith a preselected offset “d” of the longitudinal weld seams in anindustrial field and with as constant an offset “d” as possible, withthe result that the manufacturing process produces a set of tailoredtubular blanks with the same offset. These are also tubes 30, or rathertailored tubular blanks, which are made up of different tube parts 36and 37.

FIGS. 5 a and 5 b show another exemplary embodiment similar to the onein FIGS. 3 a and 3 b, in which, however, the tailored blank 40 is madeup of three metal sheets 41, 42 and 43, to which end the weld seams 44and 45 are provided. Corresponding interfaces 46-49 are constructed inthe case of the tailored tubular blank 50 with its longitudinal weldseam 51. Here, too, all three metal sheets 41-43 may have differentthicknesses and/or material characteristics or two of the metal sheets,say 41 and 43, may be identical sheets and metal sheet 42 may be a sheetwith different characteristics. This can result, for instance followingthe reshaping of the tailored tubular blanks 50, for example by means ofhydroforming, in a side rail that exhibits high strength at its centreand a lower strength, or desired upsetting behaviour, at its ends.Naturally, too, just one of the seams 44 and 45 may run diagonally andthe other seam may run straight, as in the prior art, and thus intersectthe longitudinal seam if that is what is wanted.

FIGS. 6 a and 6 b show another exemplary embodiment in which thetailored blank 60 is once again made up of three metal sheets, with oneseam 65 in this case forming a longitudinal weld seam on thecorresponding tailored tubular blank 69 and the obliquely situated weldseam 64 forming the circumferential seam. The metal seams 65, 62 and 63may in turn exhibit different thicknesses and material characteristicsand, as in the examples already depicted, the interfaces 66 and 67 whichare created in the case of the tailored tubular blanks have the statedadvantages over an intersecting path of the weld seams under the priorart.

FIG. 7 shows another tailored blank in which it is readily apparent thatin this instance the interfaces 74 and 75 of the weld seam 73 whichconnects the metal sheets 71 and 72 lie at a right angle to thelongitudinal weld seam in the case of the tailored tubular blanks. Thismay be referred to as a T-shaped joint, although this designation mayalso be used for the other interfaces in accordance with the inventioneven if the seams do not meet exactly at right angles.

FIG. 8 shows another example of a tailored blank 80 with three weldedmetal sheets 81, 82 and 83, the interfaces of the weld seams 84 and 86likewise exhibiting a predetermined offset from the longitudinal weldseam along the longitudinal weld seam of the can body constituted bythis tailored blank, or by tailored tubular blanks to be weldedsubsequently, and forming a non-intersecting joint with the longitudinalweld seam. In place of metal sheet 83 it would also be possible toprovide a recess that forms a recess on the tailored tubular blank.

Although this invention has been shown and described with respect to thedetailed embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and the scope of the invention

1. Tailored tubular blank with at least one circumferential weld seamand at least one longitudinal weld seam, characterised in that thecircumferential seam and the longitudinal seam do not intersect oneanother when they meet at the joint.
 2. Tailored tubular blank accordingto claim 1, characterised in that the longitudinal seam is continuous.3. Tailored tubular blank according to claim 1, characterised in thatthe circumferential seam is continuous.
 4. Tailored tubular blankaccording to claim 1, characterised in that the interfaces of the seamsare arranged a preselected distance apart from one another.
 5. Tailoredtubular blank according to claim 1, characterised in that it isconstituted from metal sheets with different characteristics.
 6. Set ofa plurality of industrially fabricated tailored tubular blanks ofidentical construction having at least one circumferential weld seam andat least one longitudinal weld seam, characterised in that thecircumferential seam and the longitudinal seam meet a joint and theinterfaces are spaced a preselected distance apart from one anotherwhich is the same for all the tailored tubular blanks of the set. 7.Process for making tailored tubular blanks each of which has at leastone circumferential weld seam and at least one longitudinal weld seam,characterised in that the circumferential seam and the longitudinal seamare arranged in such a manner that the seams meet at a joint.
 8. Processaccording to claim 7, characterised in that the interfaces are apreselected distance apart from one another.
 9. Process according toclaim 7, characterised in that a tailored blank having at least one weldseam is made, that from the tailored blank a can body is formed, withthe weld seam arranged in such a way or the tubular can body shapingdone in such a way that the ends of the weld seam on the mutuallyopposing can body edges are spaced apart from another and that theopposing can body edges are joined by a continuous longitudinal weldseam.
 10. Process according to claim 7, characterised in that at leasttwo tubes are welded with longitudinal seams, the tubes notably beingtubes having different thicknesses and/or characteristics of the metalsheets, and that the tubes with longitudinal seams offset relative toone another are joined to one another by a continuous circumferentialweld seam.
 11. A tailored tubular blank, comprising: at least onecircumferential weld seam, having a first end and a second end; and atleast one longitudinal weld seam; wherein the first end of thecircumferential weld seam intersects the longitudinal weld seam at afirst intersection point and the second end of the circumferential weldseam intersects the longitudinal weld seam at a second intersectionpoint, and the first intersection point is separated from the secondintersection point.
 12. The tailored tubular blank of claim 11, whereinthe longitudinal seam is continuous.
 13. The tailored tubular blank ofclaim 11, wherein the circumferential seam extends continuously betweenthe first end and the second end.
 14. The tailored tubular blank ofclaim 11, wherein the first intersection point and the secondintersection point are separated by a preselected distance.
 15. Thetailored tubular blank of claim 11, comprising metal sheets withdifferent characteristics joined together by the weld seams.
 16. Amethod for making tailored tubular blanks, comprising the steps of:providing a plurality of metal sheets; joining the plurality of metalsheets along at least one circumferential weld seam, the circumferentialweld seam having a first end and a second end; joining the plurality ofmetal sheets along at least one longitudinal weld seam; and positioningthe circumferential weld seam and the longitudinal weld seam so that thefirst end of the circumferential weld seam intersects the longitudinalweld seam at a first intersection point and the second end of thecircumferential weld seam intersects the longitudinal weld seam at asecond intersection point, and the first intersection point is separatedfrom the second intersection point.
 17. The method of claim 16, whereinthe circumferential weld seam and the longitudinal weld seam arepositioned so that the first intersection point and the secondintersection point are separated by a preselected distance.